1. Field of the Invention
This invention relates to a liquid crystal display of the type known, e.g. from J. Appl. Phys., Vol. 53, No. 12 (December 1982), pages 8599 to 8606.
2. Description of the Prior Art
This liquid crystal display described in the above-noted reference functions according to the bistability effect and consists of a cell with two plane-parallel glass plates separated by means of spacers at the border of the cell and bonded together on only two sides. The distance between the glass plates is about 15 .mu.m. It is expressly mentioned that dust particles in the cell and disturbances on the surface of the glass plates are unfavorable for such a display. These phenomena accelerate the disappearance of the displayed information, which is unavoidable with these driving methods. The display must therefore be constantly refreshed.
The display cell is located between two crossed polarizers. Electrode layers and orientation layers formed over the electrode layers are provided on the inner surfaces of the glass plates. The orientation layers are produced by oblique vacuum deposition of SiO at a 5.degree. angle to the plate plane. As a result, the adjoining liquid crystal molecules are aligned with a tilt angle of 55.degree. perpendicular to the plate. The directions of orientation of the orientation layers are either parallel or perpendicular to the transmission axes of the polarizers. A cyanobiphenyl mixture E7 with the chiral additive cholesteryl nonanoate is filled into the cell as the liquid crystal. The internal twist angle of the liquid crystal is 360.degree.; the ratio between layer thickness and pitch is 0.983. A range of from 0.95 to 1.10 is regarded as appropriate for this ratio. Below 0.95, the switching times are very long, so that this range is to be excluded for such a display. Moreover, the aim is for flawless bistable action of the display, for which layer thickness and pitch ought to be about the same. The display is driven either according to the 3:1 addressing scheme or according to the 2:1 addressing scheme in both of which the writing is done line-at-a-time. Since the display must be constantly refreshed, only a few lines can be written. This means that the degree of multiplexing is low and that a dot matrix display with a large number of lines is not achievable according to the above reference.